Chrysostom points to the number of reasons St Paul adduces to lead his readers and hearers away from error. In the first place he points to the utter folly, having become free, of wanting to become slaves again; in the second, he reminds them that they would be ungrateful to their benefactor, despising the one who frees them and preferring the one who enslaved them; and finally, he points out the absurdity of it, because the Law had no power over those saved by Christ.
Theodoret notes that at this stage (verse 13) Paul shifts to ethical exhortations and his commendation of the practice of virtue ‘For it was not in order to sin without fear that we have been freed from the Law’. It is clear from this that he is commending the observance of the moral law, and above all, love.
St Augustine notes that the works of the law pertain to the new covenant, but adds that Paul is pointing out that those who do good works in Christ do so not because of fear of the consequences of disobedience, but for love of Christ. The Jews fulfil certain works of the law which consist in ceremonies ‘but are completely unable to to fulfil those that consist in good conduct. For nothing fulfils these except love’.
Chrysostom adds that Paul shows how we can fulfil the law – in love and in loving and serving one another. Love of strife, faction, ambition are the causes of error, and from these things we can be rescued by being slaves to one another in love. The law is not fulfilled in circumcision but in love. It is the proper function of the human spirit to govern the flesh, but, as Augustine reminds us, it sometimes makes slow headway against the flesh. All Christian struggle with sin and the old Adam, but the aim is to make virtue a second nature – we obey the law spiritually when we act out of love, not fear, but remembering that the law is there for our good too, and, as Jerome points out, the patriarchs were saved under it. But as Augustine comments, only the resurrection can complete sanctification.